Method and apparatus for receiving downlink reference signal in wireless communication system

ABSTRACT

The present disclosure relates to a pre-5 th -Generation (5G) or 5G communication system to be provided for supporting higher data rates Beyond 4 th -Generation (4G) communication system such as Long Term Evolution (LTE). A method for operating a terminal in a wireless communication system, the method comprises determining a time-frequency structure of a downlink reference signal, and receiving, from a base station, the downlink reference signal according to the time-frequency structure.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 16/337,337,which is a 371 National Stage of International Application No.PCT/KR2017/010708, filed Sep. 27, 2017, which claims priority to ChinesePatent Application No. 201610857538.3, filed Sep. 27, 2016, and ChinesePatent Application No. 201610867885.4 filed Sep. 29, 2016, thedisclosures of which are herein incorporated by reference in theirentirety.

BACKGROUND 1. Field

The present disclosure generally relates to a wireless communication,and in particular to a method and apparatus for receiving downlinkreference signal in the wireless communication system.

2. Description of Related Art

To meet the demand for wireless data traffic having increased sincedeployment of 4^(th) generation (4G) communication systems, efforts havebeen made to develop an improved 5^(th) generation (5G) or pre-5Gcommunication system. Therefore, the 5G or pre-5G communication systemis also called a ‘Beyond 4G Network’ or a ‘Post Long Term Evolution(LTE) System’.

The 5G communication system is considered to be implemented in higherfrequency (mmWave) bands, e.g., 28 GHz or 60 GHz bands, so as toaccomplish higher data rates. To decrease propagation loss of the radiowaves and increase the transmission distance, the beamforming, massivemultiple-input multiple-output (MIMO), Full Dimensional MIMO (FD-MIMO),array antenna, an analog beam forming, large scale antenna techniquesare discussed in 5G communication systems.

In addition, in 5G communication systems, development for system networkimprovement is under way based on advanced small cells, cloud RadioAccess Networks (RANs), ultra-dense networks, device-to-device (D2D)communication, wireless backhaul, moving network, cooperativecommunication, Coordinated Multi-Points (CoMP), reception-endinterference cancellation and the like.

In the 5G system, Hybrid frequency shift keying (FSK) and quadratureamplitude modulation (FQAM) and sliding window superposition coding(SWSC) as an advanced coding modulation (ACM), and filter bank multicarrier (FBMC), non-orthogonal multiple access (NOMA), and sparse codemultiple access (SCMA) as an advanced access technology have beendeveloped.

A reference signal is not for delivering any specific information. Thepurpose of this reference signal is to deliver the reference point forthe downlink power. Another important role of reference signal is tohelp the receiver demodulate the received signal. Since the referencesignal is made up of data known to both transmitter and receiver, thereceiver can figure out how the communication channel distort the databy comparing the decoded received reference signal and predefinedreference signal, and use the result of this comparison to equalize(post process) the received user data. The process for the receiver toperform this comparison and figure out the characteristics of acommunication channel is called ‘channel estimation’ which is one of themost critical part of LTE. These reference signal are carried bymultiples of specific resource elements in each slots and the locationof the resource elements are specifically determined by antennaconfiguration.

SUMMARY

In physical resources with orthogonal frequency division multiplexing(OFDM) symbols having different characteristic, such as differences ofcyclic prefix (CP), differences of carrier frequency, differences ofsubcarrier width and so on, and in the premises of the demodulationperformance requirement being achieved, since the transmitted downlinkreference signal occupies more resources, resources cannot be taken fulladvantage of.

According to various embodiments of the present disclosure, a method foroperating a terminal in a wireless communication system, the methodcomprises determining a time-frequency structure of a downlink referencesignal, and receiving, from a base station, the downlink referencesignal according to the time-frequency structure.

According to various embodiments of the present disclosure, an apparatusfor a terminal in a wireless communication system comprises atransceiver configured to transmit and receive signals and at least oneprocessor. The at least one processor determines a time-frequencystructure of a downlink reference signal of a transmitted data, andcontrols to the transceiver to receive the downlink reference signalaccording to the time-frequency structure.

Various embodiments of the present disclosure provide apparatus andmethod for receiving downlink reference signal efficiently in wirelesscommunication systems.

The additional aspects and advantages of the invention will be providedin the description below in part, and it will be apparent from thefollowing description, or be learned from the practice of the presentdisclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or additional aspects and advantages of the presentdisclosure will be apparent and easily comprehensible from the followingdescription for the embodiments in accompanied with the figures,wherein,

FIG. 1 illustrates a wireless communication system according to variousembodiments of the present disclosure;

FIG. 2 illustrates the BS in the wireless communication system accordingto various embodiments of the present disclosure;

FIG. 3 illustrates the terminal in the wireless communication systemaccording to various embodiments of the present disclosure;

FIG. 4 illustrates the communication interface in the wirelesscommunication system according to various embodiments of the presentdisclosure;

FIG. 5 is a schematic diagram of a frame structure of time divisionduplex (TDD) system of long term evolution (LTE);

FIG. 6 is a schematic diagram of resources of orthogonal frequencydivision multiplexing (OFDM) symbols with subcarriers width being 15 kHzand 30 kHz in one carrier;

FIG. 7 is a schematic diagram of a configuration of antenna ports 7 and8 of demodulation reference signal (DMRS);

FIG. 8 is a schematic diagram of the structure of OFDM symbols withsubcarrier width and subframe length both being different;

FIG. 9 is a schematic diagram of a first change relationship of cyclicprefix (CP) length with subcarrier width of OFDM;

FIG. 10 is a schematic diagram of a second change relationship of CPlength with subcarrier width of OFDM;

FIG. 11A is a schematic flowchart of a method for receiving downlinkreference signal in a wireless communication system according to variousembodiments of the present disclosure;

FIG. 11B is another schematic flowchart of a method for receivingdownlink reference signal in a wireless communication system accordingto various embodiments of the present disclosure;

FIG. 12 is a schematic flowchart of a method for transmitting downlinkreference signal in a wireless communication system according to variousembodiments of the present disclosure;

FIG. 13 is a schematic diagram of designing the configuration of DMRS ina wireless communication system according to various embodiments of thepresent disclosure;

FIG. 14 is a schematic diagram of designing the configuration of DMRS ina wireless communication system according to various embodiments of thepresent disclosure;

FIG. 15 is a schematic diagram of designing the configuration of DMRS ina wireless communication system according to various embodiments of thepresent disclosure;

FIG. 16 is a schematic diagram of designing the configuration of DMRS ina wireless communication system according to various embodiments of thepresent disclosure;

FIG. 17 is a schematic diagram of designing the configuration of DMRS ina wireless communication system according to various embodiments of thepresent disclosure;

FIG. 18 is a schematic diagram of the structure of DMRS in thetime-domain in a wireless communication system according to variousembodiments of the present disclosure;

FIG. 19 is another schematic diagram of the structure of DMRS in thetime-domain in a wireless communication system according to variousembodiments of the present disclosure;

FIG. 20 is a schematic diagram of the structure of DMRS in thefrequency-domain in a wireless communication system according to variousembodiments of the present disclosure;

FIG. 21 is a schematic diagram of the structure of DMRS in thefrequency-domain in a wireless communication system according to variousembodiments of the present disclosure;

FIG. 22 is a schematic diagram of the structure of DMRS in thefrequency-domain in a wireless communication system according to variousembodiments of the present disclosure;

FIG. 23 is a schematic diagram of the structure of DMRS in thefrequency-domain in a wireless communication system according to variousembodiments of the present disclosure;

FIG. 24 is a block diagram of the apparatus for receiving downlinkreference signal in a wireless communication system according to variousembodiments of the present disclosure;

FIG. 25 is another block diagram of the apparatus for receiving downlinkreference signal in a wireless communication system according to variousembodiments of the present disclosure.

DETAILED DESCRIPTION

The terms used in the present disclosure are only used to describespecific embodiments, and are not intended to limit the presentdisclosure. As used herein, singular forms may include plural forms aswell unless the context clearly indicates otherwise. Unless definedotherwise, all terms used herein, including technical and scientificterms, have the same meanings as those commonly understood by a personskilled in the art to which the present disclosure pertains. Such termsas those defined in a generally used dictionary may be interpreted ashaving the meanings equal to the contextual meanings in the relevantfield of art, and are not to be interpreted as having ideal orexcessively formal meanings unless clearly defined in the presentdisclosure. In some cases, even terms defined in the present disclosureshould not be interpreted as excluding embodiments of the presentdisclosure.

Hereinafter, in various embodiments of the present disclosure, hardwareapproaches will be described as an example. However, various embodimentsof the present disclosure include a technology that uses both hardwareand software and thus, the various embodiments of the present disclosuremay not exclude the perspective of software.

Hereinafter, the present disclosure describes technology for receivingdownlink reference signal in a wireless communication system.

Terms used in the following descriptions, such as a term referring tovariables that determine time-frequency structure of the downlinkreference signal, the terms referring to a signal, the terms referringto a channel, the terms referring to control information, the termsreferring to a network entity, and the terms referring to elements of adevice used in the following description are used only for convenienceof the description. Accordingly, the present disclosure is not limitedto the following terms, and other terms having the same technicalmeaning may be used.

Further, although the present disclosure describes various embodimentsbased on the terms used in some communication standards (for example,3rd Generation Partnership Project (3GPP)), they are only examples forthe description. Various embodiments of the present disclosure may beeasily modified and applied to other communication systems.

Embodiments of the present disclosure will be described in detailhereinafter. The examples of these embodiments have been illustrated inthe accompanying drawings throughout which same or similar referencenumerals refer to same or similar elements or elements having same orsimilar functions. The embodiments described with reference to theaccompanying drawings are illustrative, merely used for explaining thepresent disclosure and should not be regarded as any limitationsthereto.

It can be understood by those skilled in the art, unless otherwisedefined, all terms (including technical and scientific terms) usedherein have the same meaning as commonly understood by one of ordinaryskill in the art to which this invention belongs. It should be furtherunderstood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

What need to be illustrated is that the present disclosure provides amethod for receiving downlink reference signal, in other words, themethod for receiving downlink reference signal can be achieved, by beingprogramed, as a manner of computer program being realized in the relateddevices of user equipment (UE), provided the method is described in theview of UE.

FIG. 1 illustrates a wireless communication system according to variousembodiments of the present disclosure. In FIG. 1 , a base station (BS)110, a terminal 120, and a terminal 130 are illustrated as the part ofnodes using a wireless channel in a wireless communication system. FIG.1 illustrates only one BS, but another BS, which is the same as orsimilar to the BS 110, may be further included.

The BS 110 is network infrastructure that provides wireless access tothe terminals 120 and 130. The BS 110 has coverage defined as apredetermined geographical region based on the distance at which asignal can be transmitted. The BS 110 may be referred to as “accesspoint (AP),” “eNodeB (eNB),” “5th generation (5G) node,” “wirelesspoint,” “transmission/reception Point (TRP)” as well as “base station.”

Each of the terminals 120 and 130 is a device used by a user, andperforms communication with the BS 110 through a wireless channel.Depending on the case, at least one of the terminals 120 and 130 mayoperate without user involvement. That is, at least one of the terminals120 and 130 is a device that performs machine-type communication (MTC)and may not be carried by the user. Each of the terminals 120 and 130may be referred to as “user equipment (UE),” “mobile station,”“subscriber station,” “remote terminal,” “wireless terminal,” or “userdevice” as well as “terminal.”

The BS 110, the terminal 120, and the terminal 130 may transmit andreceive wireless signals in millimeter wave (mmWave) bands (for example,28 GHz, 30 GHz, 38 GHz, and 60 GHz). At this time, in order to improve achannel gain, the BS 110, the terminal 120, and the terminal 130 mayperform beamforming. The beamforming may include transmissionbeamforming and reception beamforming. That is, the BS 110, the terminal120, and the terminal 130 may assign directivity to a transmissionsignal and a reception signal. To this end, the BS 110 and the terminals120 and 130 may select serving beams 112, 113, 121, and 131 through abeam search procedure or a beam management procedure. After that,communications may be performed using resources having a quasico-located relationship with resources carrying the serving beams 112,113, 121, and 131.

A first antenna port and a second antenna ports are considered to bequasi co-located if the large-scale properties of the channel over whicha symbol on the first antenna port is conveyed can be inferred from thechannel over which a symbol on the second antenna port is conveyed. Thelarge-scale properties may include one or more of delay spread, dopplerspread, doppler shift, average gain, average delay, and spatial Rxparameters.

FIG. 2 illustrates the BS in the wireless communication system accordingto various embodiments of the present disclosure. A structureexemplified at FIG. 2 may be understood as a structure of the BS 110.The term “-module”, “-unit” or “-er” used hereinafter may refer to theunit for processing at least one function or operation and may beimplemented in hardware, software, or a combination of hardware andsoftware.

Referring to FIG. 2 , the BS may include a wireless communicationinterface 210, a backhaul communication interface 220, a storage unit230, and a controller 240.

The wireless communication interface 210 performs functions fortransmitting and receiving signals through a wireless channel. Forexample, the wireless communication interface 210 may perform a functionof conversion between a baseband signal and bitstreams according to aphysical layer standard of the system. For example, in datatransmission, the wireless communication interface 210 generates complexsymbols by encoding and modulating transmission bitstreams. Further, indata reception, the wireless communication interface 210 reconstructsreception bitstreams by demodulating and decoding the baseband signal.

In addition, the wireless communication interface 210 up-converts thebaseband signal into an Radio Frequency (RF) band signal, transmits theconverted signal through an antenna, and then down-converts the RF bandsignal received through the antenna into the baseband signal. To thisend, the wireless communication interface 210 may include a transmissionfilter, a reception filter, an amplifier, a mixer, an oscillator, adigital-to-analog convertor (DAC), an analog-to-digital convertor (ADC),and the like. Further, the wireless communication interface 210 mayinclude a plurality of transmission/reception paths. In addition, thewireless communication interface 210 may include at least one antennaarray consisting of a plurality of antenna elements.

On the hardware side, the wireless communication interface 210 mayinclude a digital unit and an analog unit, and the analog unit mayinclude a plurality of sub-units according to operation power, operationfrequency, and the like. The digital unit may be implemented as at leastone processor (e.g., a digital signal processor (DSP)).

The wireless communication interface 210 transmits and receives thesignal as described above. Accordingly, the wireless communicationinterface 210 may be referred to as a “transmitter” a “receiver,” or a“transceiver.” Further, in the following description, transmission andreception performed through the wireless channel may be used to have ameaning including the processing performed by the wireless communicationinterface 210 as described above.

The backhaul communication interface 220 provides an interface forperforming communication with other nodes within the network. That is,the backhaul communication interface 220 converts bitstreams transmittedto another node, for example, another access node, another BS, a highernode, or a core network, from the BS into a physical signal and convertsthe physical signal received from the other node into the bitstreams.

The storage unit 230 stores a basic program, an application, and datasuch as setting information for the operation of the BS 110. The storageunit 230 may include a volatile memory, a non-volatile memory, or acombination of volatile memory and non-volatile memory. Further, thestorage unit 230 provides stored data in response to a request from thecontroller 240.

The controller 240 controls the general operation of the BS. Forexample, the controller 240 transmits and receives a signal through thewireless communication interface 210 or the backhaul communicationinterface 220. Further, the controller 240 records data in the storageunit 230 and reads the recorded data. The controller 240 may performsfunctions of a protocol stack that is required from a communicationstandard. According to another implementation, the protocol stack may beincluded in the wireless communication interface 210. To this end, thecontroller 240 may include at least one processor.

According to exemplary embodiments of the present disclosure, thecontroller 240 may synthesize the influencing factors, and determine,according to different conditions, the designing methods of demodulationreference signal (DMRS) in time-domain and frequency-domain. Forexample, the controller 240 may control the base station to performoperations according to the exemplary embodiments of the presentdisclosure.

FIG. 3 illustrates the terminal in the wireless communication systemaccording to various embodiments of the present disclosure. A structureexemplified at FIG. 3 may be understood as a structure of the terminal120 or the terminal 130. The term “-module”, “-unit” or “-er” usedhereinafter may refer to the unit for processing at least one functionor operation, and may be implemented in hardware, software, or acombination of hardware and software.

Referring to FIG. 3 , the terminal 120 includes a communicationinterface 310, a storage unit 320, and a controller 330.

The communication interface 310 performs functions fortransmitting/receiving a signal through a wireless channel. For example,the communication interface 310 performs a function of conversionbetween a baseband signal and bitstreams according to the physical layerstandard of the system. For example, in data transmission, thecommunication interface 310 generates complex symbols by encoding andmodulating transmission bitstreams. Also, in data reception, thecommunication interface 310 reconstructs reception bitstreams bydemodulating and decoding the baseband signal. In addition, thecommunication interface 310 up-converts the baseband signal into an RFband signal, transmits the converted signal through an antenna, and thendown-converts the RF band signal received through the antenna into thebaseband signal. For example, the communication interface 310 mayinclude a transmission filter, a reception filter, an amplifier, amixer, an oscillator, a DAC, and an ADC.

Further, the communication interface 310 may include a plurality oftransmission/reception paths. In addition, the communication interface310 may include at least one antenna array consisting of a plurality ofantenna elements. In the hardware side, the wireless communicationinterface 210 may include a digital circuit and an analog circuit (forexample, a radio frequency integrated circuit (RFIC)). The digitalcircuit and the analog circuit may be implemented as one package. Thedigital circuit may be implemented as at least one processor (e.g., aDSP). The communication interface 310 may include a plurality of RFchains. The communication interface 310 may perform beamforming.

The communication interface 310 transmits and receives the signal asdescribed above. Accordingly, the communication interface 310 may bereferred to as a “transmitter,” a “receiver,” or a “transceiver.”Further, in the following description, transmission and receptionperformed through the wireless channel is used to have a meaningincluding the processing performed by the communication interface 310 asdescribed above.

The storage unit 320 stores a basic program, an application, and datasuch as setting information for the operation of the terminal 120. Thestorage unit 320 may include a volatile memory, a non-volatile memory,or a combination of volatile memory and non-volatile memory. Further,the storage unit 320 provides stored data in response to a request fromthe controller 330.

The controller 330 controls the general operation of the terminal 120.For example, the controller 330 transmits and receives a signal throughthe communication interface 310. Further, the controller 330 recordsdata in the storage unit 320 and reads the recorded data. The controller330 may performs functions of a protocol stack that is required from acommunication standard. According to another implementation, theprotocol stack may be included in the communication interface 310. Tothis end, the controller 330 may include at least one processor ormicroprocessor, or may play the part of the processor. Further, the partof the communication interface 310 or the controller 330 may be referredto as a communication processor (CP). According to various embodiments,the controller 330 may includes a determination module. Here, thedetermination module may be a command/code temporarily resided in thecontroller 330, a storage space that stores the command/code, or a partof circuitry of the controller 330.

According to exemplary embodiments of the present disclosure, thecontroller 330 may determine time-frequency structure of a downlinkreference signal of transmitted data and determine the method forreceiving downlink reference signal corresponding to the higher layersignaling indication. For example, the controller 330 may control theterminal to perform operations according to the exemplary embodiments ofthe present disclosure.

FIG. 4 illustrates the communication interface in the wirelesscommunication system according to various embodiments of the presentdisclosure. FIG. 4 shows an example for the detailed configuration ofthe communication interface 210 of FIG. 2 or the communication interface310 of FIG. 3 . More specifically, FIG. 4 shows elements for performingbeamforming as part of the communication interface 210 of FIG. 2 or thecommunication interface 310 of FIG. 3 .

Referring to FIG. 4 , the communication interface 210 or 310 includes anencoding and circuitry 402, a digital circuitry 404, a plurality oftransmission paths 406-1 to 406-N, and an analog circuitry 408.

The encoding and circuitry 402 performs channel encoding. For thechannel encoding, at least one of a low-density parity check (LDPC)code, a convolution code, and a polar code may be used. The encoding andcircuitry 402 generates modulation symbols by performing constellationmapping.

The digital circuitry 404 performs beamforming for a digital signal (forexample, modulation symbols). To this end, the digital circuitry 404multiples the modulation symbols by beamforming weighted values. Thebeamforming weighted values may be used for changing the size and phraseof the signal, and may be referred to as a “precoding matrix” or a“precoder.” The digital circuitry 404 outputs the digitally beamformedmodulation symbols to the plurality of transmission paths 406-1 to406-N. At this time, according to a multiple input multiple output(MIMO) transmission scheme, the modulation symbols may be multiplexed,or the same modulation symbols may be provided to the plurality oftransmission paths 406-1 to 406-N.

The plurality of transmission paths 406-1 to 406-N convert the digitallybeamformed digital signals into analog signals. To this end, each of theplurality of transmission paths 406-1 to 406-N may include an inversefast Fourier transform (IFFT) calculation unit, a cyclic prefix (CP)insertion unit, a DAC, and an up-conversion unit. The CP insertion unitis for an orthogonal frequency division multiplexing (OFDM) scheme, andmay be omitted when another physical layer scheme (for example, a filterbank multi-carrier: FBMC) is applied. That is, the plurality oftransmission paths 406-1 to 406-N provide independent signal processingprocesses for a plurality of streams generated through the digitalbeamforming. However, depending on the implementation, some of theelements of the plurality of transmission paths 406-1 to 406-N may beused in common.

The analog circuitry 408 performs beamforming for analog signals. Tothis end, the digital circuitry 404 multiples the analog signals bybeamforming weighted values. The beamformed weighted values are used forchanging the size and phrase of the signal. More specifically, accordingto a connection structure between the plurality of transmission paths406-1 to 406-N and antennas, the analog circuitry 408 may be configuredin various ways. For example, each of the plurality of transmissionpaths 406-1 to 406-N may be connected to one antenna array. In anotherexample, the plurality of transmission paths 406-1 to 406-N may beconnected to one antenna array. In still another example, the pluralityof transmission paths 406-1 to 406-N may be adaptively connected to oneantenna array, or may be connected to two or more antenna arrays.

The wireless communication system according to various embodiments ofthe present disclosure can support two duplex manners, specifically,frequency division duplex (FDD) and time division duplex (TDD). Thetransmission of long term evolution (LTE) comprises a transmission frombase station (eNB) to user equipment (UE) (denoted as downlink) and atransmission from UE to base station (denoted as uplink). For TDDsystem, the uplink and downlink are transmitted on the same carrier atdifferent times; while, for FDD system, the uplink and downlink aretransmitted on different carries respectively.

FIG. 5 is a schematic diagram of a frame structure of TDD system of LTE.Wherein, the length of each radio frame is 10 ms, which is divided intotwo half-frames of length being 5 ms, wherein, each half-frame compriseseight time slots of length being 0.5 ms and three special fields oflength being 1 ms. The three special fields respectively are downlinkpilot time slot (DwPTS), guard period (GP) and uplink pilot time slot(UpPTS). And more, each subframe is composed of two continuous timeslots.

Based on the frame structure of FIG. 5 , within each 10 ms, the uplinkand the downlink share ten subframes, and each subframe is configured touplink or is configured to downlink, wherein, the subframe configured tothe uplink is called as uplink frame, and the subframe configured to thedownlink is called as downlink subframe. Seven type of uplink ordownlink configuration is supported in the TDD system, as shown in theFIG. 5 , wherein, D denotes downlink subframe, U denotes uplinksubframe, and S denotes a special subframe comprising the above threespecial fields. Each subframe comprises fourteen OFDM symbols, the widthof subcarrier is 15 kHz, each physical resource block (PRB) comprisestwelve subcarriers, the frequency field width of each PRB is 180 kHz.

TABLE 1 Uplink or Downlink Configuration of TDD Config- Transitionuration point Subframe index number period 0 1 2 3 4 5 6 7 8 9 0  5 ms DS U U U D S U U U 1  5 ms D S U U D D S U U D 2  5 ms D S U D D D S U DD 3 10 ms D S U U U D D D D D 4 10 ms D S U U D D D D D D 5 10 ms D S UD D D D D D D 6 10 ms D D U U U D S U U D

The downlink data is transmitted through physical downlink sharedchannel (PDSCH), wherein, hybrid automatic retransmissionrequest-acknowledgement (HARQ) information of the PDSCH can betransmitted on physical uplink shared channel (PUSCH) or physical uplinkcontrol channel (PUCCH). The uplink data is transmitted through PUSCH.PDSCH and PUSCH are scheduled by physical downlink control channel orenhanced physical downlink control channel (PDCCH/EPDCCH).

When demodulating PDSCH data, it can use demodulation reference signal(DMRS) to perform channel estimation, specifically, as shown in FIG. 7 ,which is a schematic diagram of configurations of antenna ports 7 and 8of DMRS.

Due to the differences of carrier frequency used by UEs for transmittingdata, differences of movement speed of UEs, differences of size ofcells, and differences of service delay and reliability requirement,subcarrier width used for transmitting data may be different, cyclicprefix (CP) length of OFDM symbol for transmitting data may bedifferent. The differences of subcarrier width or CP length of OFDMsymbol of physical resources are collectively called as difference ofnumerology, for example, as shown in FIG. 6 , which is a schematicdiagram of resources of OFDM symbols with subcarriers widths being 15kHz and 30 kHz respectively in a carrier. Herein, the subcarrier widthmay be referred as ‘subcarrier spacing’ or ‘subcarrier space’. Besides,due to differences of subcarrier widths of OFDM symbol, the length ofsubframes may be different either. As shown in FIG. 8 , when thesubcarrier width of an OFDM symbol is 15 kHz, the subframe length is 1ms; when the subcarrier width of an OFDM symbol is 30 kHz, the subframelength is 0.5 ms, and the number of OFDM symbols are the same in eachsubframe, i.e., fourteen. Herein, the subframe may be referred as a‘slot’. The CP length and the subcarrier width of OFDM symbol arechanged into inverse proportion, in other words, when the subcarrierwidth of an OFDM symbol is 15 kHz, the CP length is 4.67 μs, when thesubcarrier width of an OFDM symbol is 30 kHz, the CP length is 2.34 μs,at this time, the overhead of CP is unchanged, in other words, theproportion of the time-frequency resource for transmitting CP and thetime-frequency resource for transmitting data is unchanged. As shown inFIG. 9 , wherein, the overhead of CP indicates a ratio of CP length tothe length of OFDM symbol. Or, when the subcarrier width of an OFDMsymbol is changed, the CP length is unchanged, that is, when thesubcarrier width of an OFDM symbol is 15 kHz, the CP length is 4.67 μs,when the subcarrier width of OFDM symbol is 30 kHz, the CP length is4.67 μs, at this moment, the overhead of CP is increased, as shown inFIG. 10 .

Wherein, the UE receives the downlink reference signal throughdetermining the time-frequency structure of downlink reference signal ofthe transmitted data by the UE and further according to thetime-frequency structure. In other words, the present scheme candetermine the time-frequency structure of the downlink reference signalto receive the downlink reference signal, so as to take full advantageof the downlink reference signal to optimize the resources.

FIG. 11A is a schematic flowchart of a method for receiving downlinkreference signal in a wireless communication system according to variousembodiments of the present disclosure. To make the objectives, technicalscheme and advantages of the present application clearer, the presentdisclosure will be illustrated in details further, with reference toaccompanying drawings and embodiments. Specifically, the methodcomprises the following steps.

Referring FIG. 11A, in Step 1101, the UE determines the time-frequencystructure of downlink reference signal of the transmitted data.Specifically, the time-frequency structure of the downlink referencesignal comprises the resource element (RE) number occupied by thedownlink reference signal in time-domain in each subframe, and theposition occupied by the downlink reference signal in time-domain. Thetime-frequency structure of the downlink reference signal furthercomprises the RE number occupied by the downlink reference signal infrequency-domain in each subframe, and the position occupied by thedownlink reference signal in frequency-domain. In step 1102, accordingto the time-frequency structure, the UE receives the downlink referencesignal.

Further, in another embodiment of the present disclosure, before thestep 1101, the method further comprises step 1100, as shown in the FIG.11B. In step 1100, according to the higher layer signaling indicationreceived from the base station, the UE determines the method forreceiving downlink reference signal corresponding to the higher layersignaling indication.

FIG. 12 is a schematic flowchart of a method for transmitting downlinkreference signal in a wireless communication system according to variousembodiments of the present disclosure. To make the objectives, technicalscheme and advantages of the present application clearer, the presentdisclosure will be illustrated in details further, with reference toaccompanying drawings and embodiments. Specifically, the methodcomprises the following steps.

Referring FIG. 12 in Step 1201, the base station determines thetime-frequency structure of downlink reference signal of thetransmitting data. Specifically, the time-frequency structure of thedownlink reference signal comprises the resource element (RE) numberoccupied by the downlink reference signal in time-domain in eachsubframe, and the position occupied by the downlink reference signal intime-domain. The time-frequency structure of the downlink referencesignal further comprises the RE number occupied by the downlinkreference signal in frequency-domain in each subframe, and the positionoccupied by the downlink reference signal in frequency-domain. In step1202, according to the time-frequency structure, the base transmits thedownlink reference signal.

Further, in another embodiment of the present disclosure, before thestep 1201, the method further comprises step 1200. In step 1200, thebase station transmits higher layer signaling indication which indicatesmethod for transmitting downlink reference signal.

The DMRS in the invention is one type of the downlink reference signals,the following description will take DMRS as an example, while, themethod in the present disclosure can also be applied to other downlinkreferences signals.

For easy to understand the concrete implements of the scheme of theinvention, the scheme of the invention will be described in detailsaccompanying with the specific embodiments below.

Embodiment 1

Specifically, the invention designs a scheme of DMRS according tospecific application scenarios, on basis of this scheme, then accordingto the preset physical features of the transmitted data, changes thefrequency-domain density and time-domain density of the DMRS, todetermine the time-frequency structure of the DMRS. Wherein, the presetphysical features of the transmitted data comprise at least one of thefollowing: the subframe length; the subcarrier width of OFDM; the CPlength; the size of carrier frequency; the service type of thetransmitted data and the movement speed of UE. Further, thefrequency-domain density of DMRS denotes the frequency interval betweenadjacent REs of DMRSs in frequency-domain, and the time-domain densitydenotes the time interval between adjacent REs of DMRSs in time-domain.

Specifically, in one application scenario of one embodiment of thescheme, according to a condition when the subframe length being 1 ms andeach subframe having fourteen OFDM symbols, subcarrier width of whichbeing 15 kHz, a DMRS scheme is designed. Because of the subframe lengthof existing LTE being 1 ms and each subframe having fourteen OFDMsymbols, subcarrier width of which being 15 kHz, the parameters ofexisting LTE are same with above parameters, thus the scheme of DMRS canuse a scheme which is same with DMRS scheme of LTE, as shown in FIG. 7 ;alternatively, according to requirements, the DMRS is put in theforemost OFDM symbols of the subframe, so as to reduce the delay of dataprocessing as far as possible.

Some methods of designing DMRS in this embodiment are described below.

Designing Method 1:

In an application scenario of the scheme, when the carrier frequency ofthe transmitted data increases by a large extent, for example, when thedata is transmitted at millimeter wave, since the data is transmittedmainly by perpendicular incidence or reflecting at millimeter wave, thedelay spread is much decreased, so that the frequency selectivity isreduced, and the frequency-domain density of DMRS can be reduced.Because of wave length of millimeter wave being very short, then theDoppler is increased, thus, the time selectivity is improved, thetime-domain density of DMRS is needed to be improved. Since frequencyoffset error and phase noise in millimeter wave have a heavy influenceon the demodulation performance, increasing the width of OFDM subcarriercan against the influence of frequency offset error and phase noise inmillimeter wave on the demodulation performance. When the subframelength is in inverse proportion with the subcarrier width, then CPlength is in inverse proportion with the subcarrier width. It is assumedthat the subcarrier changes from Δf1 to Δf1·2 m, then the length ofsubframe changes from 1 to ½m, and then the CP length changes from cp tocp/2 m. For example, in the condition of high carrier frequency, anOFDM, of which the subcarrier width is 30 kHz, the subframe length is0.5 ms and the CP length is 2.34 μs, wherein, each subframe comprisingfourteen OFDM symbols, is introduced, as shown in FIG. 13 .

Further, since the CP length becomes smaller, then frequency selectivityof channel is decreased, so as to reduce the frequency-domain density ofDMRS, that is, to increase the frequency interval between adjacent REsof DMRSs in frequency-domain. Since the subcarrier width of OFDM symbolsincreases, if the REs number between adjacent REs of DMRSs infrequency-domain maintains unchanged, then the frequency intervalbetween adjacent REs of DMRSs in frequency-domain is increased. As shownin FIG. 14 , for example, in the condition of high carrier frequency,the subcarrier width of the introduced OFDM is 30 kHz, which is doubled;the length of subframe is 0.5 ms, which is reduced by half; the lengthof CP is 2.34 μs, which is reduced by half; each subframe comprisingfourteen OFDM symbols and maintaining the REs number between adjacentREs of DMRSs in frequency-domain unchanged, then the frequency intervalbetween adjacent REs of DMRSs in frequency-domain is doubled. The REsnumber between adjacent REs of DMRSs in frequency-domain will changewith the change of CP overhead. If the CP overhead is unchanged, the REsnumber between adjacent REs of DMRSs in frequency-domain maintainsunchanged, for example, with the increasing of CP overhead, the REsnumber between adjacent REs of DMRSs in frequency-domain decreases, inother words, with the increasing of CP overhead, the frequencyselectivity of channel enhances, further the DMRS frequency-domaindensity increases.

Further, because of the increasing of carrier frequency and decreasingof wave length, the time selectivity of channel is increased. It needsto improve the time-domain density of DMRS, in other words, to decreasethe time interval between adjacent REs of DMRSs in time-domain. Sincethe duration time of each OFDM symbol is decreased, if the REs numberbetween adjacent REs of DMRSs in time-domain maintains unchanged, thetime interval between adjacent REs of DMRSs in time-domain is decreased.As shown in FIG. 14 , for example, in the condition of high carrierfrequency, the subcarrier width of the introduced OFDM is 30 kHz, whichis doubled; the subframe length is 0.5 ms, which is reduced by half; theCP length is 2.34 μs, which is reduced by half; each subframe comprisesfourteen OFDM symbols and the REs number between adjacent REs of DMRSsin time-domain maintained unchanged, then the time interval betweenadjacent REs of DMRSs in time-domain is doubled.

Designing Method 2:

In an application scenario of the scheme, when the carrier frequency fortransmitting data increases by a large extent, for example, when thedata is transmitted at millimeter wave, since the data is transmittedmainly by perpendicular incidence or reflecting at millimeter wave, thedelay spread is much decreased, so that the frequency selectivity isreduced, and the frequency-domain density of DMRS can be reduced.Because of wave length of millimeter wave being very short, then theDoppler is increased, thus, the time selectivity is improved, thetime-domain density of DMRS is needed to improve. Since frequency offseterror and phase noise at millimeter wave have a heavy influence on thedemodulation performance, increasing the subcarrier width of OFDM symbolcan against the influence of frequency offset error and phase noise atmillimeter wave on the demodulation performance. When the subframelength is in inverse proportion with the subcarrier width, then CPlength is in inverse proportion with the subcarrier width. It is assumedthat the subcarrier width changes from Δf1 to Δf1·2 m, then the subframelength changes from 1 to ½m, then the CP length changes from cp to cp/2m. For example, in the condition of high carrier frequency, an OFDM, ofwhich the subcarrier width is 30 kHz, the subframe length is 0.5 ms andthe CP length is 2.34 μs, wherein, each subframe comprises fourteen OFDMsymbols, is introduced, which is changed into that as shown in FIG. 13 .

Further, since the CP length becomes smaller, then frequency selectivityof channel is decreased, so as to reduce the frequency-domain density ofDMRS, that is, to increase the frequency interval between adjacent REsof DMRSs in frequency-domain. Since the subcarrier width of OFDM symbolsincreases, if the REs number between adjacent REs of DMRSs infrequency-domain maintains unchanged, then the frequency intervalbetween adjacent REs of DMRSs in frequency-domain is increased. As shownin FIG. 15 , for example, in the condition of high carrier frequency,the subcarrier width of the introduced OFDM is 30 kHz, which is doubled;the subframe length is 0.5 ms, which is reduced by half; the CP lengthis 2.34 μs, which is reduced by half; each subframe comprises fourteenOFDM symbols and the REs number between adjacent REs of DMRSs infrequency-domain is maintained unchanged, then the frequency intervalbetween adjacent REs of DMRSs in frequency-domain is doubled.

Further, because of the increasing of carrier frequency and decreasingof wave length, the time selectivity of channel may be increased; sincethe movement speed of UE decreases, the time selectivity of channel maybe decreased, for the influences of the above two factors, it is no needto improve the time-domain density of DMRS, that is, the time intervalbetween adjacent REs of DMRSs in time-domain should be maintained. Sincethe duration time of each OFDM symbol is decreased, if the time intervalbetween adjacent REs of DMRSs in time-domain maintains unchanged, theREs number between adjacent REs of DMRSs in time-domain is increased. Asshown in FIG. 15 , for example, in the condition of high carrierfrequency, the subcarrier width of the introduced OFDM is 30 kHz, whichis doubled; the subframe length is 0.5 ms, which is reduced by half; theCP length is 2.34 μs, which is reduced by half; each subframe comprisesfourteen OFDM symbols, wherein, the duration time of each OFDM symbolreduces by half, and maintaining the REs number between adjacent REs ofDMRSs in frequency-domain double, then the time interval betweenadjacent REs of DMRSs in time-domain will be unchanged.

Designing Method 3:

In an application scenario of the scheme, when the coverage area forservicing cells reduces by a large extent and radius of cells decrease,the frequency selectivity is reduced, resulting in reducing thefrequency-domain density of DMRS. Since the carrier frequency isunchanged, the time selectivity is unchanged, so that the time-domaindensity is maintained. Because of the requirement of low delay service,the increasing of width of OFDM subcarrier can reduce the length of OFDMsymbol. When the length of subframe changes in inverse proportion withthe change of width of subcarrier, then length of CP changes in inverseproportion with the change of width of subcarrier. It is assumed thatthe width of subcarrier changes from Δf1 to Δf1·2 m, then the length ofsubframe changes from 1 to ½m, then the length of CP changes from cp tocp/2 m. For example, an OFDM, of which the width of subcarrier is 30kHz, the length of subframe is 0.5 ms and the length of CP is 2.34 ms,wherein, each subframe comprises fourteen OFDM symbols, is introduced,which is changed into that as shown in FIG. 13 .

Further, since the length of CP becomes smaller, then frequencyselectivity of channel is decreased, so as to reduce thefrequency-domain density of DMRS, that is, to increase the frequencyinterval between adjacent REs of DMRSs in frequency-domain. Since thewidth of subcarrier of OFDM symbols increases, if the REs number betweenadjacent REs of DMRSs in frequency-domain maintains unchanged, then thefrequency interval between adjacent REs of DMRSs in frequency-domain isincreased. As shown in FIG. 15 , for example, in the condition of highcarrier frequency, the width of subcarrier of the introduced OFDM is 30kHz, which is doubled; the length of subframe is 0.5 ms, which isreduced by half; the length of CP is 2.34 μs, which is reduced by half;each subframe comprises fourteen OFDM symbols and the REs number betweenadjacent REs of DMRSs in frequency-domain is maintained unchanged, thenthe frequency interval between adjacent REs of DMRSs in frequency-domainis doubled.

Further, because of carrier frequency being unchanged, the timeselectivity of channel is unchanged. It needs to improve the time-domaindensity of DMRS, in other words, the time interval between adjacent REsof DMRSs in time-domain should be maintained. Since the duration time ofeach OFDM symbol is decreased, if the time interval between adjacent REsof DMRSs in time-domain maintains unchanged, the REs number betweenadjacent REs of DMRSs in time-domain is increased. As shown in FIG. 15 ,for example, the width of subcarrier of the introduced OFDM is 30 kHz,which is doubled; the length of subframe is 0.5 ms, which is reduced byhalf; the length of CP is 2.34 μs, which is reduced by half; eachsubframe comprises fourteen OFDM symbols, the duration time of each OFDMsymbol reduces by half and maintaining the REs number between adjacentREs of DMRSs in frequency-domain double, then the time interval betweenadjacent REs of DMRSs in time-domain will be unchanged.

Designing Method 4:

In an application scenario of the scheme, when the coverage area forservicing cells is unchanged, radius of cells is unchanged, and thefrequency selectivity is unchanged, thus, the frequency selectivity isunchanged, resulting in the frequency-domain density of DMRS beingmaintained. Since the carrier frequency is unchanged, the timeselectivity is unchanged, so that the time-domain density is maintained.Because of the requirement of low delay service, the increasing of widthof OFDM subcarrier can reduce the length of OFDM symbol. When the lengthof subframe changes in inverse proportion with the change of width ofsubcarrier, since the delay spread is unchanged, the length of CP isunchanged, it is assumed that the width of subcarrier changes from Δf1to Δf1·2 m, then the length of subframe changes from 1 to ½m, then thelength of CP changes is unchanged. For example, an OFDM, of which thewidth of subcarrier is 30 kHz, the length of subframe is 0.5 ms and thelength of CP is 4.67 μs, is introduced.

Further, since the length of CP maintains unchanged, then frequencyselectivity of channel is unchanged, so as to maintain thefrequency-domain density of DMRS, that is, to maintain the frequencyinterval between adjacent REs of DMRSs in frequency-domain. Since thewidth of subcarrier of OFDM symbols increases, if the frequency intervalbetween adjacent REs of DMRSs in frequency-domain maintains unchanged,then the REs number between adjacent REs of DMRSs in frequency-domain isdecreased. In other words, in the condition of same number ofsubcarrier, the RE number of DMRS in frequency is increased. As shown inFIG. 16 , for example, the width of subcarrier of the introduced OFDM is30 kHz, which is doubled; the length of subframe is 0.5 ms, which isreduced by half; the length of CP is 4.67 μs, which is unchanged; thefrequency interval between adjacent REs of DMRSs in frequency-domain ismaintained unchanged, then the REs number between adjacent REs of DMRSsin frequency-domain will be reduced by half.

Further, because of carrier frequency being unchanged, the timeselectivity of channel is unchanged. It needs to improve the time-domaindensity of DMRS, in other words, the time interval between adjacent REsof DMRSs in time-domain should be maintained. Since the duration time ofeach OFDM symbol is decreased, if the time interval between adjacent REsof DMRSs in time-domain maintains unchanged, the REs number between REsof DMRSs in adjacent time-domain is increased. As shown in FIG. 16 , forexample, the width of subcarrier of the introduced OFDM is 30 kHz, whichis doubled; the length of subframe is 0.5 ms, which is reduced by half;the length of CP is 4.67 μs, which is unchanged; the time intervalbetween adjacent REs of DMRSs in time-domain is maintained unchanged.

Designing Method 5:

In an application scenario of the scheme, when the coverage area forservicing cells is unchanged, radius of cells is unchanged, and thefrequency selectivity is unchanged, thus, the frequency selectivity isunchanged, resulting in the frequency-domain density of DMRS beingmaintained. Since the carrier frequency is unchanged, the timeselectivity is unchanged, so that the time-domain density of DMRS ismaintained. Because of the requirement of low delay service, theincreasing of width of OFDM subcarrier can reduce the length of OFDMsymbol. When the length of subframe changes in inverse proportion withthe change of width of subcarrier, since the delay spread is unchanged,the length of CP is unchanged, it is assumed that the width ofsubcarrier changes from Δf1 to Δf1·2 m, then the length of subframechanges from 1 to ½m, then the length of CP is unchanged. For example,an OFDM, of which the width of subcarrier is 30 kHz, the length ofsubframe is 0.5 ms and the length of CP is 4.67 μs, is introduced.

Further, since the length of CP maintains unchanged, then frequencyselectivity of channel is unchanged, so as to maintain thefrequency-domain density of DMRS, that is, to maintain the frequencyinterval between adjacent REs of DMRSs in frequency-domain. Since thewidth of subcarrier of OFDM symbols increases, if the frequency intervalbetween adjacent REs of DMRSs in frequency-domain maintains unchanged,then the REs number between adjacent REs of DMRSs in frequency-domain isdecreased. In other words, in the condition of same number ofsubcarrier, the RE number of DMRS in frequency-domain is increased. Asshown in FIG. 17 , for example, the width of subcarrier of theintroduced OFDM is 30 kHz, which is doubled; the length of subframe is0.5 ms, which is reduced by half; the length of CP is 4.67 μs, which isunchanged; the frequency interval between adjacent REs of DMRSs infrequency-domain is maintained unchanged, then the REs number betweenadjacent REs of DMRSs in frequency-domain is reduced.

Further, because of carrier frequency being unchanged, while, themovement speed of UE is improved and the time selectivity of channel isincreased, it needs to improve the time-domain density of DMRS, in otherwords, the time interval between adjacent REs of DMRSs in time-domainshould be decreased. Since the duration time of each OFDM symbol isdecreased, if the time interval between adjacent REs of DMRSs intime-domain maintains is decreased, the REs number between adjacent REsof DMRSs in time-domain is maintained unchanged. As shown in FIG. 17 ,for example, the width of subcarrier of the introduced OFDM is 30 kHz,which is doubled; the length of subframe is 0.5 ms, which is reduced byhalf; the length of CP is 4.67 μs, which is unchanged; the REs numberbetween adjacent REs of DMRSs in time-domain is maintained unchanged.

In summary, the above five designing methods of DMRS is determinedaccording to the preset physical features of transmitted data, such as,the subframe length, the subcarrier width of the used OFDM, the CPlength, the size of carrier, the service type of transmission and themovement speed of UE. When the subcarrier width or the CP length of OFDMchange, because there are many influencing factors and functions ofcertain factors are conflicting, therefore, the base station cansynthesize the influencing factors, and determine one of the designingmethod from designing method 1, designing method 2, designing method 3,designing method 4 and designing method 5 as the designing method ofDMRS. The UE can determine, through receiving higher layer signalingindication, one of the designing method 1, designing method 2, designingmethod 3, designing method 4 and designing method 5 to receive DMRS, andthen perform channel estimation.

For the configuration of time-frequency structure of DMRS,frequency-domain density and time-domain density can be determinedaccording to the number of resource elements, which is unrelated to thetime-domain length of OFDM symbol and the subcarrier width of OFDMsymbol. For example, in the FIG. 14 , the configuration of thetime-frequency structure of DMRS in left picture and the configurationof the time-frequency structure of DMRS in the right picture can beregarded as the same configuration, in spite of the width of OFDMsubcarrier in the left picture being 15 kHz, the width of OFDMsubcarrier in the right picture being 30 kHz, and the length oftime-domain of OFDM in the left picture being as twice as that in theright picture.

Embodiment 2

In one embodiment of the scheme, the base station can determine,according to different conditions, the designing methods of DMRS intime-domain and frequency-domain, and UE can determine, throughreceiving the higher layer signaling indication from the base station,one of the above the designing methods of DMRS in time-domain andfrequency-domain to receive DMRS, then the UE can perform channelestimation.

Specifically, for the requirement of time-domain density of DMRS,resources of DMRS must be included within each subframe, that is, whenthe length of subframe is shorten further, to ensure that resources ofDMRS must be included within each subframe, the time-domain density ofDMRS cannot be decreased further. For example, when the subframe lengthis 0.5 ms, DMRS in each subframe in time-domain is not repeated, whenthe length of subframe is 0.25 ms, density of DMRS in each subframe intime-domain maintain unchanged. Or, several types of structure of DMRSin time-domain are designed, for example, structure 1 and structure 2are designed as shown in FIG. 18 , which is designed according to theREs number in time-domain, and is unrelated to the length of OFDMsymbol; as shown in FIG. 19 , the design in the left side and the designin the right side are the same type of time-domain designing structure.

Further, for the requirements of frequency-domain density of DMRS,resources of DMRS must be included within each physical resource block(PRB). At present, the alternative numbers of subcarriers are 12 and 16in each PRB, and it need to further consider which one of 12 and 16would be selected as the number of subcarriers in each PRB infrequency-domain. With the increasing of width of OFDM subcarrier,according to the change of frequency selectivity, several types offrequency-domain structure of DMRS can be designed, for example, whenthe number of subcarriers in each PRB is 12, the frequency-domaininterval of DMRS in each PRB can be one or more of 4, 2 and 1. Such as,the designing structure 1, structure 2 and structure 3 are shown as FIG.20 , which is designed according to the REs number in thefrequency-domain and unrelated with the subcarrier width of OFDM symbol,as shown in FIG. 21 , the design on the left side and the design on theright side are the same type of frequency-domain designing structure.When the number of subcarriers in each PRB is 16, the frequency-domaininterval of DMRS in each PRB can be one or more of 4, 2 and 1, such as,the designing structure 1, structure 2 and structure 3, as shown in FIG.22 , which is designed according to REs number in frequency-domain andunrelated with the subcarrier width of OFDM symbol; while, as shown inFIG. 23 , the design on the left side and the design on the right sideare the same frequency-domain structure designing.

For the time-frequency structure of DMRS for receiving common data(e.g., master information block (MIB), system information block (SIB) orpaging information), the UE may not in connected mode, at this moment,the UE cannot receive higher layer signaling configuration information,and the time-frequency structure of DMRS can determine a default DMRSstructure according to protocols; or the time-frequency structure of theDMRS can be indicated according to the information carried on thereceived synchronization signal; or the time-frequency structure of DMRScan be determined according to one or more factors of the subcarrierwidth of OFDM, the CP length, the CP overhead and the size of carrierfrequency, which are acquired according to received synchronizationsignal, for example, as shown in Table 2, which is the mappingrelationship between the time-frequency structure of DMRS for receivingcommon data, the subcarrier width of OFDM and the CP length.

TABLE 2 the mapping relationship between the time-frequency structure ofDMRS, the CP length and the subcarrier width of OFDM the subcarrierwidth the time-frequency the CP length of OFDM structure of DMRS the CPlength 1 the subcarrier width 1 the time-frequency structure 1 of OFDMof DMRS the CP length 2 the subcarrier width 2 the time-frequencystructure 2 of OFDM of DMRS . . . . . . . . . the CP length N thesubcarrier width N the time-frequency structure of OFDM N of DMRS

For example, as shown in Table 3, the mapping relationship between thefrequency-domain structure of DMRS for receiving common data and the CPoverhead of OFDM.

TABLE 3 the mapping relationship of the frequency-domain structurebetween DMRS and the CP overhead of OFDM the CP overhead thefrequency-domain structure of DMRS the CP overhead 1 thefrequency-domain structure 1 of DMRS the CP overhead 2 thefrequency-domain structure 2 of DMRS . . . . . . the CP overhead N thefrequency-domain structure N of DMRS

For the time-frequency structure of DMRS for receiving the UE specificdata, it can be determined according to the above method, or determinedby the UE through receiving higher layer signaling configuration.

For the time-frequency structure of DMRS for receiving physical downlinkcontrol channel (PDCCH), it can be processed according to the followingmethod. PDCCH can be divided into common search space and UE specificsearch space. For the DMRS of PDCCH for common search space and/or thetime-frequency structure of DMRS of PDCCH for UE specific search space,the time-frequency structure of DMRS can determine a default DMRSstructure according to protocols; or the time-frequency structure of theDMRS can be indicated according to the information carried on thereceived synchronization signal or system information; or thetime-frequency structure of DMRS can be determined according to one ormore factors of the subcarrier width of OFDM, the CP length, the CPoverhead and the size of carrier frequency, which are acquired accordingto received synchronization signal.

Or, for the time-frequency structure of DMRS for UE specific searchspace PDCCH, which can be determined by UE according to the higher layersignaling configuration.

In summary, in one embodiment of the present disclosure, a method forreceiving downlink reference signal is provided, which determines thetime-frequency structure of downlink reference signal of the transmitteddata by UE, and then, according to the time-frequency structure, the UEreceives the downlink reference signal. In other words, the scheme candetermine the time-frequency structure of downlink reference signal toreceive the downlink reference signal, so as to take full advantages ofthe downlink reference signal and optimize the resources.

Further, according to the functional modularity thoughts of computersoftware, on basis of above method for receiving downlink referencesignal, the invention further provides a device for receiving downlinkreference signal, which can be a user equipment. Specifically, as shownin FIG. 24 , the device comprises a determination module 2401 and afirst receiving module 2402.

Wherein, the determination module 2401 is configured to determinetime-frequency structure of a downlink reference signal of transmitteddata by UE; the first receiving module 2402 is configured to, accordingto the time-frequency structure, receive the downlink reference signalby UE.

Further, in one embodiment of the scheme, the device for receivingdownlink reference signal further comprises a second receiving module2400, as shown in FIG. 25 . Wherein, the second receiving module 2400 isconfigured to, before determining a time-frequency structure of adownlink reference signal of a transmitted data by the determinationmodule 2401, according to a higher layer signaling indication receivedfrom a base station, determine a method for receiving downlink referencesignal corresponding to the high signaling indication by UE.

In the scheme of present disclosure, the implements of specific functionof each module in the device for receiving downlink reference signal canrefer to the specific steps of above Step 1100, Step 1101, Step 1102,embodiment 1 and embodiment 2, and will not be repeated here.

The foregoing descriptions are merely some implementations of thepresent disclosure. It should be noted that, to a person of ordinaryskill in the art, various improvements and modifications can be madewithout departing from the principle of the present disclosure, andthese improvements and modifications shall be regarded as falling intothe protection scope of the present disclosure.

Methods according to embodiments stated in claims and/or specificationsof the present disclosure may be implemented in hardware, software, or acombination of hardware and software.

When the methods are implemented by software, a computer-readablestorage medium for storing one or more programs (software modules) maybe provided. The one or more programs stored in the computer-readablestorage medium may be configured for execution by one or more processorswithin the electronic device. The at least one program may includeinstructions that cause the electronic device to perform the methodsaccording to various embodiments of the present disclosure as defined bythe appended claims and/or disclosed herein.

The programs (software modules or software) may be stored innon-volatile memories including a random access memory and a flashmemory, a read only memory (ROM), an electrically erasable programmableread only memory (EEPROM), a magnetic disc storage device, a compactdisc-ROM (CD-ROM), digital versatile discs (DVDs), or other type opticalstorage devices, or a magnetic cassette. Alternatively, any combinationof some or all of the may form a memory in which the program is stored.Further, a plurality of such memories may be included in the electronicdevice.

In addition, the programs may be stored in an attachable storage devicewhich is accessible through communication networks such as the Internet,Intranet, local area network (LAN), wide area network (WAN), and storagearea network (SAN), or a combination thereof. Such a storage device mayaccess the electronic device via an external port. Further, a separatestorage device on the communication network may access a portableelectronic device.

In the above-described detailed embodiments of the present disclosure, acomponent included in the present disclosure is expressed in thesingular or the plural according to a presented detailed embodiment.However, the singular form or plural form is selected for convenience ofdescription suitable for the presented situation, and variousembodiments of the present disclosure are not limited to a singleelement or multiple elements thereof. Further, either multiple elementsexpressed in the description may be configured into a single element ora single element in the description may be configured into multipleelements.

While the present disclosure has been shown and described with referenceto certain embodiments thereof, it will be understood by those skilledin the art that various changes in form and details may be made thereinwithout departing from the scope of the present disclosure. Therefore,the scope of the present disclosure should not be defined as beinglimited to the embodiments, but should be defined by the appended claimsand equivalents thereof.

Although the present disclosure has been described with an exemplaryembodiment, various changes and modifications may be suggested to oneskilled in the art. It is intended that the present disclosure encompasssuch changes and modifications as fall within the scope of the appendedclaims.

What is claimed is:
 1. A method performed by a terminal in a wirelesscommunication system, the method comprising: identifying a firsttime-frequency resource of a first demodulation reference signal for amaster information block (MIB) based on information carried onsynchronization signals; receiving, from a base station, the firstdemodulation reference signal for the MIB based on the firsttime-frequency resource; and receiving, from the base station, a seconddemodulation reference signal for a physical downlink shared channel(PDSCH) based on a configuration information for a second time-frequencyresource of the second demodulation reference signal, wherein theconfiguration information for the second time-frequency resource of thesecond demodulation reference signal is received via a higher layersignaling.
 2. The method of claim 1, further comprising: obtaining asubcarrier spacing of a synchronization signal based on thesynchronization signal; and determining a subcarrier spacing for thefirst time-frequency resource of the first demodulation reference signalas the obtained subcarrier spacing of the synchronization signal.
 3. Themethod of claim 1, further comprising: performing first channelestimation based on the received first demodulation reference signal;obtaining the MIB based on a result of the first channel estimation;performing second channel estimation based on the second demodulationreference signal; and obtaining data on the PDSCH based on a result ofthe second channel estimation.
 4. The method of claim 1, wherein, when asubcarrier spacing for each resource element (RE) of the secondtime-frequency resource of the second demodulation reference signal ischanged, a frequency-domain density and a time-domain density aremaintained and a length of cyclic prefix (CP) is changed, wherein thefrequency-domain density comprises frequency intervals between adjacentREs of downlink reference signals in a frequency-domain, and wherein thetime-domain density comprises time intervals between adjacent REs ofdownlink reference signals in a time-domain.
 5. A method performed by abase station in a wireless communication system, the method comprising:transmitting, to a terminal, synchronization signals; transmitting, tothe terminal, a first demodulation reference signal for a masterinformation block (MIB) based on a first time-frequency resource,wherein the first time-frequency resource are identified based oninformation carried on the synchronization signals; and transmitting, tothe terminal, a second demodulation reference signal for a physicaldownlink shared channel (PDSCH) based on a configuration information fora second time-frequency resource of the second demodulation referencesignal, wherein the configuration information for the secondtime-frequency resource of the second demodulation reference signal istransmitted via a higher layer signaling.
 6. The method of claim 5,further comprising: configuring the first time-frequency resource of thefirst demodulation reference signal based on a subcarrier spacing of asynchronization signal.
 7. The method of claim 5, further comprising:transmitting the MIB with the first demodulation reference signal on afirst channel; and transmitting data on the PDSCH with the seconddemodulation reference signal on a second channel.
 8. The method ofclaim 5, wherein, when a subcarrier spacing for each resource element(RE) of the second time-frequency resource of the second demodulationreference signal is changed, a frequency-domain density and atime-domain density are maintained and a length of a cyclic prefix (CP)is changed, wherein the frequency-domain density comprises frequencyintervals between adjacent REs of downlink reference signals in afrequency-domain, and wherein the time-domain density comprises timeintervals between adjacent REs of downlink reference signals in atime-domain.
 9. A terminal in a wireless communication system, theterminal comprising: at least one transceiver; and at least oneprocessor coupled with the at least one transceiver, wherein the atleast one processor is configured to: identify a first time-frequencyresource of a first demodulation reference signal for a masterinformation block (MIB) based on information carried on synchronizationsignals, receive, from a base station, the first demodulation referencesignal for the MIB based on the first time-frequency resource, andreceive, from the base station, a second demodulation reference signalfor a physical downlink shared channel (PDSCH) based on a configurationinformation for a second time-frequency resource of the seconddemodulation reference signal, wherein the configuration information forthe second time-frequency resource of the second demodulation referencesignal is received via a higher layer signaling.
 10. The terminal ofclaim 9, wherein the at least one processor is further configured to:obtain a subcarrier spacing of a synchronization signal based on thesynchronization signal; and determine a subcarrier spacing for the firsttime-frequency resource of the first demodulation reference signal asthe obtained subcarrier spacing of the synchronization signal.
 11. Theterminal of claim 9, wherein the at least one processor is furtherconfigured to: perform a first channel estimation based on the receivedfirst demodulation reference signal; obtain the MIB based on a result ofthe first channel estimation; perform a second channel estimation basedon the received second demodulation reference signal; and obtain data onthe PDSCH based on a result of the second channel estimation.
 12. Theterminal of claim 9, wherein, when a subcarrier spacing for eachresource element (RE) of the second time-frequency resource of thesecond demodulation reference signal is changed, a frequency-domaindensity and a time-domain density are maintained and a length of acyclic prefix (CP) is changed, wherein the frequency-domain densitycomprises frequency intervals between adjacent REs of downlink referencesignals in a frequency-domain, and wherein the time-domain densitycomprises time intervals between adjacent REs of downlink referencesignals in a time-domain.
 13. A base station in a wireless communicationsystem, the base station comprising: at least one transceiver; and atleast one processor coupled with the at least one transceiver, whereinthe at least one processor is configured to: transmit, to a terminal,synchronization signals transmit, to the terminal, a first demodulationreference signal for a master information block (MIB) based on a firsttime-frequency resource, wherein the first time-frequency resource areidentified based on information carried on the synchronization signals,and transmit, to the terminal, a second demodulation reference signalfor a physical downlink shared channel (PDSCH) based on a configurationinformation for a second time-frequency resource of the seconddemodulation reference signal, wherein the configuration information forthe second time-frequency resource of the second demodulation referencesignal is transmitted via a higher layer signaling.
 14. The base stationof claim 13, wherein the at least one processor is further configured toconfigure the first time-frequency resource of the first demodulationreference signal based on a subcarrier spacing of a synchronizationsignal.
 15. The base station of claim 13, wherein the at least oneprocessor is further configured to: transmit the MIB with the firstdemodulation reference signal on a first channel; and transmit data onthe PDSCH with the second demodulation reference signal on a secondchannel.
 16. The base station of claim 13, wherein, when a subcarrierspacing for each resource element (RE) of the second time-frequencyresource of the second demodulation reference signal is changed, afrequency-domain density and a time-domain density are maintained and alength of cyclic prefix (CP) is changed, wherein the frequency-domaindensity comprises frequency intervals between adjacent REs of downlinkreference signals in a frequency-domain, and wherein the time-domaindensity comprises time intervals between adjacent REs of downlinkreference signals in a time-domain.